Semiconductor device

ABSTRACT

A semiconductor device includes a latch circuit including a first inverter configured to output a first signal based on an input signal, a second inverter configured to output a first clock signal based on a first strobe signal, a third inverter configured to output a second clock signal based on a second strobe signal, a first clock generation circuit configured to generate a third clock signal having transitions that are delayed with respect to the first clock signal, a second clock generation circuit configured to generate a fourth clock signal having transitions that are delayed with respect to the second clock signal, a fourth inverter configured to output an inversion signal of the first signal in accordance with the third and fourth clock signals, and a data latch circuit configured to latch an output signal of the fourth inverter.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.17/473,012, filed Sep. 13, 2021, which application is a continuation ofU.S. patent application Ser. No. 17/000,708, filed Aug. 24, 2020, nowU.S. Pat. No. 11,121,710, issued Sep. 14, 2021, which application is adivisional of U.S. patent application Ser. No. 16/571,023, filed Sep.13, 2019, now U.S. Pat. No. 10,784,866, issued Sep. 22, 2020, whichapplication is a divisional of U.S. patent application Ser. No.15/907,264, filed Feb. 27, 2018, now U.S. Pat. No. 10,461,750, issuedOct. 29, 2019, which application is based upon and claims the benefit ofpriority from Japanese Patent Application No. 2017-126189, filed Jun.28, 2017, the entire contents of which are incorporated herein byreference.

FIELD

Embodiments described herein relate generally to a semiconductor device.

BACKGROUND

A semiconductor device in which a core chip is stacked on an interfacechip provided on a semiconductor substrate, through a through-siliconvia (TSV) is known.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a semiconductor device accordingto a first embodiment.

FIG. 2 is a sectional view illustrating the semiconductor deviceaccording to the first embodiment.

FIG. 3 is a block diagram illustrating an interface chip in thesemiconductor device according to the first embodiment.

FIG. 4 is a block diagram illustrating a data input circuit in theinterface chip in the semiconductor device according to the firstembodiment.

FIG. 5 is a circuit diagram illustrating a latch circuit for data inputin the semiconductor device according to the first embodiment.

FIG. 6 is a timing chart illustrating various signals and a potential ofa node in the latch circuit for data input in the semiconductor deviceaccording to the first embodiment.

FIG. 7 is a circuit diagram illustrating a latch circuit for data inputaccording to a comparative example.

FIG. 8 is a timing chart illustrating various signals and a potential ofa node in the latch circuit for data input according to the comparativeexample.

FIG. 9 is a circuit diagram illustrating a latch circuit for data inputin a semiconductor device according to a second embodiment.

FIG. 10 is a timing chart illustrating various signals and potentials oftwo nodes in the latch circuit for data input in the semiconductordevice according to the second embodiment.

FIG. 11 is a timing chart illustrating various signals and potentials oftwo nodes in the comparative example.

FIG. 12 is a circuit diagram illustrating a latch circuit for data inputin a semiconductor device according to a third embodiment.

FIG. 13 is a timing chart illustrating various signals and potentials oftwo nodes in the latch circuit for data input in the semiconductordevice according to the third embodiment.

FIG. 14 is a timing chart illustrating the various signals and thepotentials of the two nodes in the latch circuit for data input in thesemiconductor device according to the third embodiment.

FIG. 15 is a timing chart illustrating an example of the various signalsand the potentials of the two nodes in the latch circuit for data input.

FIG. 16 is a timing chart illustrating an example of the various signalsand the potentials of the two nodes in the latch circuit for data input.

FIG. 17 is a circuit diagram illustrating a latch circuit for data inputin a semiconductor device according to a fourth embodiment.

DETAILED DESCRIPTION

Embodiments provide a semiconductor device in which it is possible toimprove processing speed.

In general, according to one embodiment, there is a semiconductor devicewhich includes an input/output (IO) signal receiver circuit and a latchcircuit. The latch circuit includes a first inverter configured tooutput a first signal based on an input signal received from the IOsignal receiver circuit, a second inverter configured to output a firstclock signal based on a first strobe signal, a third inverter configuredto output a second clock signal based on a second strobe signal which isan inversion signal of the first strobe signal, a first clock generationcircuit a first clock generation circuit which is connected to an outputterminal of the second inverter and is configured to generate a thirdclock signal from the first clock signal, wherein logical leveltransitions in the third clock signal are delayed with respect to thefirst clock signal and are completed in a shorter amount of time thanthe first clock signal, a second clock generation circuit which isconnected to an output terminal of the third inverter and is configuredto generate a fourth clock signal from the second clock signal, whereinlogical level transitions in the fourth clock signal are delayed withrespect to the second clock signal and are completed in a shorter amountof time than the first clock signal, a fourth inverter configured tooutput an inversion signal of the first signal in accordance with thethird and fourth clock signals, and a data latch circuit configured tolatch an output signal of the fourth inverter in accordance with thethird and fourth clock signals.

Hereinafter, embodiments will be described with reference to thedrawings. In the descriptions, parts which are common with each other inall drawings are denoted by the same reference signs.

1. First Embodiment

A semiconductor device according to a first embodiment will bedescribed. A memory system including a NAND flash memory will bedescribed below as an example of a semiconductor device. In the firstembodiment, a high-speed memory system of a DDR type will be described.However, it is not limited thereto. The memory system in the firstembodiment may be a general memory system.

1. 1 Configuration 1. 1. 1 Overall Configuration of Memory System

First, an overall configuration of the memory system will be describedwith reference to FIG. 1 .

As illustrated in FIG. 1 , a memory system 1 includes a plurality ofNAND flash memory 100-0 to 100-N N is any integer of 1 or more), aninterface (I/F) chip 400, and a controller 200. In the first embodiment,when the NAND flash memory 100-0 to 100-N are not required to bedistinguished from one another, they will be referred to “NAND flashmemory 100”. This applies to other components as well.

The NAND flash memory 100 includes a plurality of memory cells andstores data with in a non-volatile manner. In the first embodiment, theNAND flash memory 100 includes two channels ch0 and ch1. The number ofchannels provided in the NAND flash memory 100 may be one, or three ormore or may be set to any value. The controller 200 is connected to theNAND flash memory 100 via the I/F chip 400 for each of the channels overa NAND bus. The controller 200 is connected to a host device 300 over ahost bus. The controller 200 controls the NAND flash memory 100 via theI/F chip 400 for each of the channels. The controller 200 access theNAND flash memory 100 via the I/F chip 400 for each of the channels, inresponse to a command received from the host device 300. The host device300 may be, for example, a digital camera or a personal computer. Thehost bus may be, for example, an SD® interface bus.

The NAND bus causes a signal to be transmitted and received inaccordance with a NAND interface. In the first embodiment, asillustrated in FIG. 1 , the controller 200 and the I/F chip 400 areconnected to each other over an interface having two channels. Here, acase where a NAND interface is provided for each channel will bedescribed. However, the same NAND interface may be used by the channelsby using identification information of a channel, for example.

Specific examples of the signal include a chip enable signal CEn, anaddress latch enable signal ALE, a command latch enable signal CLE, awrite enable signal WEn, a read enable signal REn, an input or outputsignal I/O, and a data strobe signal DQS.

The signal CEn is a signal used for causing the NAND flash memory 100 tobe in an enable state. The chip enable signal CEn is asserted at a lowlevel (also described as an “L” level below). The signal CLE is a signalused for notifying the NAND flash memory 100 that an input signal I/O tothe NAND flash memory 100 indicates a command. The signal ALE is asignal used for notifying the NAND flash memory 100 that an input signalI/O to the NAND flash memory 100 indicates an address. The signal WEn isa signal which is input at a transition timing when a command or anaddress is transitioned from a low level to a high level (also describedas an “H” level below). The signal REn is also asserted at a low level.The signal REn is a signal used for reading an output signal I/O fromthe NAND flash memory 100. The signal BREn is a complementary signal ofthe signal REn. The signal BREn is a signal used for reading an outputsignal I/O from the NAND flash memory 100.

The input or output signal I/O is, for example, a 8-bit signal. Theinput or output signal I/O represents an entity of data which istransmitted and received between the NAND flash memory 100 and thecontroller 200. As the input or output signal I/O, a command, anaddress, write data, data to be read, and the like are provided.

The signal DQS and a complementary signal BDQS of the signal DQS areoutput from a transmission side, along with the signal I/O. A clocksignal for adjusting a timing of inputting data by receiving the signalDQS and the signal BDQS which are transmitted is provided on a datareception side.

1. 1. 2 Configuration of NAND Flash Memory

Next, a configuration of the NAND flash memory 100 will be described.

As illustrated in FIG. 1 , the NAND flash memory 100 includes a memorycell array 110, a row decoder 120, a driver circuit 130, a senseamplifier 140, an address register 150, a command register 160, and asequencer 170.

The memory cell array 110 includes, for example, four blocks BLK (BLK0to BLK3). Each of the four blocks BLK is an assembly of a plurality ofnonvolatile memory cells which are correlated with rows and columns.Thus, the memory cell array 110 stores data assigned from the controller200.

The row decoder 120 selects any of the blocks BLK0 to BLK3 and furtherselects a row in the selected block BLK.

The driver circuit 130 supplies a voltage to the selected block BLK viathe row decoder 120.

When data is read, the sense amplifier 140 senses data read from thememory cell array 110 and performs computation required for the senseddata. Then, the sense amplifier 140 outputs the data DAT to thecontroller 200. When data is written, the sense amplifier 140 transfersdata DAT which is received from the controller 200 and is to be written,to the memory cell array 110.

The address register 150 holds an address ADD received from thecontroller 200. The command register 160 holds a command CMD receivedfrom the controller 200.

The sequencer 170 controls the entire operation of the NAND flash memory100, based on the command CMD which is held in the command register 160.

The NAND flash memory 100 may be a flat type NAND flash memory whichincludes a memory cell array 110 in which memory cells aretwo-dimensionally arranged on a semiconductor substrate, or may be athree-dimensional stacked type NAND flash memory which includes a memorycell array 110 in which memory cells are three-dimensionally arrangedabove a semiconductor substrate.

The configuration of the memory cell array 110 of the three-dimensionalstacked type NAND flash memory is disclosed, for example, in: U.S.patent application Ser. No. 12/407,403, filed on Mar. 19, 2009 andentitled “THREE DIMENSIONAL STACKED NONVOLATILE SEMICONDUCTOR MEMORY,”now U.S. Pat. No. 8,952,426; U.S. patent application Ser. No.12/406,524, filed on Mar. 18, 2009 and entitled “THREE DIMENSIONALSTACKED NONVOLATILE SEMICONDUCTOR MEMORY,” no U.S. Pat. No. 7,852,675;U.S. patent application Ser. No. 12/679,991, filed on Mar. 25, 2010 andentitled “NON-VOLATILE SEMICONDUCTOR STORAGE DEVICE AND METHOD OFMANUFACTURING THE SAME,” now U.S. Pat. No. 8,372,720; and U.S. patentapplication Ser. No. 12/532,030, filed on Mar. 23, 2009 and entitled“SEMICONDUCTOR MEMORY AND METHOD FOR MANUFACTURING SAME,” now abandoned.The entire contents of the above applications are incorporated herein byreference.

1. 1. 3 Mounting of I/F Chip and NAND Flash Memory

FIG. 2 is a sectional view illustrating a method of mounting the I/Fchip 400 and the NAND flash memory 100 in the first embodiment. FIG. 1illustrates a case of (N+1) of NAND flash memory 100. FIG. 2 illustratesa semiconductor device in which one NAND flash memory 100 is mounted ineach of eight core chips CC-1 to CC-8 (N=7).

As illustrated in FIG. 2 , the I/F chip 400 is mounted on a mountingsubstrate S. A plurality of large bumps LBP (LBP-1 to LBP-4) are formedon an upper surface of the mounting substrate S. A plurality ofmicro-bumps MBP(MBP-1 to MBP-3) are formed on an upper surface of theI/F chip 400. The large bumps LBP and the micro-bumps MBP are formed soas to cause a height from the upper surface of the substrate S to be thesame in order to stack a plurality of core chips CC (CC-1 to CC-8)thereabove.

A plurality of bumps BP(BP-1 to BP-9) are formed on a lower surface ofthe substrate S. The bumps BP are electrically connected to the largebump LBP via an interconnection formed in the substrate S. The bump BPis used transmitting and receiving an input or output signal to and fromthe outside of the substrate S. In the first embodiment, for example,the bump BP-1 is used for power and the like supplied to each of thecore chips CC-1 to CC-8. The bumps BP-2 to BP-9 are used for the inputor output signal I/O which is transferred between the controller 200 andthe I/F chip 400.

The plurality of core chips CC (CC-1 to CC-8) are stacked on the largebumps LBP and the micro-bumps MBP. The core chips CC-1 to CC-8 areelectrically connected to each other via a bump BP-A and an electrode(TSV) which penetrates the chips. Such a structure is a package typestructure which is referred to as a ball grid array (BGA) and has manyI/O pins for input and output.

FIG. 2 illustrates only the bumps BP-1 to BP-9, the large bumps LBP-1 toLBP-4, and the micro-bumps MBP-1 to MBP-4. However, a bump BP, a largebump LBP, and a micro-bump MBP which are used for other I/O signals andthe like and are not illustrated, are provided on the mounting substrateS.

According to the example in FIG. 2 , the core chips CC-2 to CC-8 aremounted on the mounting substrate in a face-up manner. The core chipCC-1 on the top layer is mounted on the core chip CC-2 in a face-downmanner. The NAND flash memory 100 described with reference to FIG. 1 isformed in each of the core chips CC (CC-1 to CC-8). The core chips CC-2to CC-8 may be mounted on the mounting substrate in a face-down manner.

Interconnection layers RDL (RDL-1 to RDL-4 and interconnection layer RDL(not illustrated)) are formed on a lower surface of the core chip CC-8that is at the bottom layer. The interconnection layer RDL electricallyconnects the large bump LBP formed on the substrate S to the TSV via apad P. The interconnection layer RDL electrically connects the largebump LBP formed on the substrate S to the micro-bump MBP.

Specifically, for example, the bump BP-1 is electrically connected toTSV via the interconnection in the substrate S, the large bump LBP-1,the interconnection layer RDL-1, and a pad P-1. For example, the bumpBP-3 is electrically connected to the I/F chip 400 via theinterconnection in the substrate S, the large bump LBP-2, theinterconnection layer RDL-2, and the micro-bump MBP-1. For example, theI/F chip 400 is electrically connected to each of the core chips CC viathe micro-bump MBP-2, the interconnection layer RDL-3, a pad P-2, andthe TSV.

The TSV is formed to penetrate the core chips CC-2 to CC-8. A TSV ineach of the core chips CC-2 to CC-8 is provided in order to cause thecore chip to be electrically connected to another core chip CC on anupper layer and/or a lower layer. The core chip CC-1 is mounted in aface-down manner. Thus, the TSV is not formed in the core chip CC-1. TheNAND flash memory 100 formed in the core chip CC-1 is electricallyconnected to a TSV in the core chip CC-2 via the bump BP-A. A TSV ineach of the core chips CC-2 to CC-8 is electrically connected to a TSVin another core chip CC on an upper layer and/or a lower layer via thebump BP-A.

1. 1. 4 Configuration of I/F Chip

Next, a configuration of the I/F chip will be described with referenceto FIG. 3 .

As illustrated in FIG. 3 , the I/F chip 400 includes an I/F circuit 500for each channel. In the first embodiment, each of the plurality of NANDflash memory 100-0 to 100-N is connected to either of the channel ch0and the channel ch1. Thus, the controller 200 can simultaneously accessthe plurality of NAND flash memory 100 via the two channels ch0 and ch1.

An I/F circuit 500-0 for the channel ch0 includes an input I/F 410-0 andan output I/F 420-0. The input I/F 410-0 is used for inputting thesignal I/O and the like from the controller 200 to the NAND flash memory100 connected to the channel ch0. The output I/F 420-0 is used foroutputting the signal I/O and the like from the NAND flash memory 100connected to the channel ch0 to the controller 200.

Similarly, an I/F circuit 500-1 for the channel ch1 includes an inputI/F 410-1 and an output I/F 420-1. The input I/F 410-1 is used forinputting the signal I/O and the like from the controller 200 to theNAND flash memory 100 for the channel ch1. The output I/F 420-1 is usedfor outputting the signal I/O and the like from the NAND flash memory100 connected to the channel ch1 to the controller 200.

The input I/F 410-0 is an interface for linking signals (CEn, ALE, CLE,WEn, REn, BREn, I/O, DQS, and BDQS) input to the channel ch0 from thecontroller 200, to the NAND flash memory 100 for the correspondingchannel ch0.

The input I/F 410-1 is an interface for linking signals (CEn, ALE, CLE,WEn, REn, BREn, I/O, DQS, and BDQS) input to the channel ch1 from thecontroller 200, to the NAND flash memory 100 for the correspondingchannel ch1.

The output I/F 420-0 is an interface for linking data (signal I/O)output from the NAND flash memory 100 for the channel ch0, to thechannel ch0 of the controller 200.

The output I/F 420-1 is an interface for linking data (signal I/O)output from the NAND flash memory 100 for the channel ch1, to thechannel ch1 of the controller 200.

1. 1. 5 Configuration of Input I/F in IF Chip

Next, a configuration of the input I/F 410 in the I/F chip 400 will bedescribed with reference to FIG. 4 . FIG. 4 illustrates a circuitconfiguration of one input I/F 410.

As illustrated in FIG. 4 , the input I/F 410 includes an input receiverIR for receiving an input signal I/O, and a latch circuit for data inputDIN (simply described as “a latch DIN” below). For example, the inputreceiver IR and the latch DIN are provided for each terminal for thesignal I/O. A signal I/O (for example, write data) input from eachterminal (pad) is stored in the latch DIN via the input receiver IR.

The latch DIN latches an input signal I/O by using the signals DQS andBDQS which are sent from the controller 200, as a trigger. In thefollowing descriptions, a period when a change of an input signal I/O isinhibited before the logical levels of the signals DQS and BDQS areinverted is referred to as “a set-up period”, and a period when thechange of an input signal I/O is inhibited after the logical levels ofthe signals DQS and BDQS are inverted is referred to as “a holdingperiod”. In the latch DIN, reducing the set-up period/holding period isrequired for improving a processing speed. Data latched by the latch DINis output to the NAND flash memory 100 which is selected by addressselection. For example, data having 8×m bits (m is any integer) isoutput to the NAND flash memory 100.

1. 1. 6 Configuration of Latch Circuit for Data Input

Next, a configuration of the latch circuit DIN for data input will bedescribed with reference to FIG. 5 . In the example in FIG. 5 , a casewhere an input signal (data) I/O is latched at a timing when the signalDQS falls and the signal BDQS rises will be described. In the followingdescriptions, one of a source and a drain of a transistor is referred toas “one end of a current path”, and the other of the source and thedrain is referred to as “the other end of the current path”. A casewhere the logical level of a signal (and node) is inverted (invertedfrom an “H” level to an “L” level or inverted from an “L” level to an“H” level) is referred to as “transitioning”. A timing at which thepotential of a signal (and node) starts to rise or fall by thetransition is referred to as “a transition start”. Further, a raisingspeed or a dropping speed of the potential when the transition of thelogical level of the signal occurs is referred to as “a transitionspeed”. A case where the transition speed is fast is referred to as aphase of “a slope of transition being steep”.

As illustrated in FIG. 5 , the latch DIN includes inverters IV1 to IV15and BT circuits BT1 and BT2.

The inverters IV1 to IV3 are connected in series. An input signal I/O isinput to an input terminal of the inverter IV1. An output terminal ofthe inverter IV3 is connected to an input terminal of the inverter IV12.An inversion signal DA of the input signal I/O, which is delayed by theinverter IV1 to IV3 which constitute three stages is input to theinverter IV12. The inverters IV1 to IV3 function as a delay circuitconfigured to generate an inversion delay signal DA of an input signalI/O. The inverter IV1 includes a p-channel MOS transistor (or alsodescribed as a PMOS transistor) P1 and an N-channel MOS transistor (oralso described as an NMOS transistor) N1. A gate of the transistor P1 isconnected to the input terminal of the inverter IV1 and a gate of thetransistor N1. A source of the transistor P1 is connected to apower-supply voltage terminal. A drain of the transistor P1 is connectedto the output terminal of the inverter IV1 and a drain of the transistorN1. The source of the transistor N1 is grounded. The inverters IV2 andIV3 have a configuration similar to that of the inverter IV1. Theinverter IV2 includes transistors P2 and N2. The inverter IV3 includestransistors P3 and N3. Although the three inverters IV1 to IV3 areconnected in series, the number of inverters which are connected inseries may be changed so long as the logical level of the signal DA isnot inverted (in this case, the number may be an odd number).

The inverters IV4 to IV6 are connected in series. The signal DQS isinput to an input terminal of the inverter IV4. An inversion delay clocksignal of the signal DQS is output from an output terminal of theinverter IV6. The output terminal of the inverter IV6 is connected to aninput terminal of the inverter IV7 and a gate of a p-channel MOStransistor P41 in the BT circuit BT1. The inverters IV4 to IV6 have aconfiguration similar to that of the inverter IV1. The inverter IV4includes transistors P4 and N4. The inverter IV5 includes transistors P5and N5. The inverter IV6 includes transistors P6 and N6. Although thethree inverters IV4 to IV6 are connected in series, the number ofinverters which are connected in series may be equal to any number ofinverters in the inverter group connected to the input terminal of theinput signal I/O.

An output terminal of the inverter IV7 is connected to a gate of ap-channel MOS transistor P13 b in the inverter IV13 and one end of acurrent path of an n-channel MOS transistor N41 in the BT circuit BT1.The inverter IV7 has a configuration similar to that of the inverter IV1and includes transistors P7 and N7.

The BT circuit BT1 includes the n-channel MOS transistor N41 and thep-channel MOS transistor P41. A gate of the transistor N41 is connectedto the power-supply voltage terminal. The other end of the current pathis connected to a drain of the transistor P41 and a gate of an n channelMOS transistor N12 b in the inverter IV12. A source of the transistorP41 is connected to the power-supply voltage terminal. A clock signalbased on the signal DQS input to the gate of the transistor N12 b isreferred to as CKn below. In the BT circuit BT1, a waveform is shaped,when an output signal of the inverter IV7 (delay clock signal of thesignal DQS) is transitioned from an “H” level to an “L” level, so as togenerate the signal CKn.

More specifically, when the output signal of the inverter IV7 has an “H”level, the input signal to the inverter IV7 has a “L” level and so thetransistor P41 is in an ON state. The transistor N41 is in a cutoffstate because a power supply voltage is applied to the gate, the source,and the drain of the transistor N41. When the output signal of theinverter IV7 is transitioned from an “H” level to an “L” level, thetransistor N41 is not in an ON state until the voltage of the outputsignal of the inverter IV7 reaches a voltage which is equal to or lowerthan ((power supply voltage)−(threshold voltage Vtn of the transistorN41)). Therefore, the transition start of the signal CKn is delayedrelative to a transition start of the output signal of the inverter IV7by a period that is correlated to a threshold voltage which is largerthan the threshold voltage Vtn of the transistor N41. Thus, the signalCKn falls to the “L” level faster than that in the output signal of theinverter IV7. That is, the transistor N41 functions as a barriertransistor for causing the start of the signal CKn falling to be delayedand causing the slope of the transition to be steep.

Accordingly, the inverters IV4 to IV7 and the BT circuit BT1 function asa generation circuit of the signal CKn.

The inverters IV8 to IV10 are connected in series. The signal BDQS isinput to an input terminal of the inverter IV8. An inversion delay clocksignal of the signal BDQS is output from an output terminal of theinverter IV10. An output terminal of the inverter IV10 is connected toan input terminal of the inverter IV11 and a gate of an n-channel MOStransistor N42 in the BT circuit BT2. The inverters IV8 to IV10 have aconfiguration similar to that of the inverter IV1. The inverter IV8includes transistors P8 and N8. The inverter IV9 includes transistors P9and N9. The inverter IV10 includes transistors P10 and N10. Although thethree inverters IV8 to IV10 are connected in series, the number ofinverters which are connected in series may be equal to any number ofinverters in the inverter group connected to the input terminal of theinput signal I/O.

An output terminal of the inverter IV11 is connected to a gate of ann-channel MOS transistor N13 b in the inverter IV13 and one end of acurrent path of a p-channel MOS transistor P42 in the BT circuit BT2.The inverter IV11 has a configuration similar to that of the inverterIV1 and includes transistors P11 and N11.

The BT circuit BT2 includes an n-channel MOS transistor N42 and ap-channel MOS transistor P42. A gate of the transistor P42 is grounded.The other end of the current path is connected to a drain of thetransistor N42 and a gate of a p channel MOS transistor P12 b in theinverter IV12. The source of the transistor N42 is grounded. A clocksignal based on the signal BDQS input to the gate of the transistor P12b is referred to as CKp below. When an output signal of the inverterIV11 (delay clock signal of the signal BDQS) is transitioned from an “L”level to an “H” level, in the BT circuit BT2, a waveform of the outputsignal of the inverter IV11 is shaped so as to generate the signal CKp.

More specifically, when the output signal of the inverter IV11 has an“L” level, the input signal to the inverter IV11 has a “H” level and sothe transistor N42 is in an ON state. The transistor P42 is in a cutoffstate because a ground voltage is applied to the gate, the source, andthe drain of the transistor P42. When the output signal of the inverterIV11 is transitioned from an “L” level to an “H” level, the transistorP42 is not in an ON state until the voltage of the output signal of theinverter IV11 reaches a voltage which is equal to or higher than athreshold voltage Vtp of the transistor P42. Therefore, the transitionstart of the signal CKp is delayed relative to a transition start of theoutput signal of the inverter IV11 by a period that is correlated to athreshold voltage which is larger than the threshold voltage Vtp of thetransistor P42. Thus, the signal CKp rises to the “H” level faster thanthat in the output signal of the inverter IV11. That is, the transistorP42 functions as a barrier transistor for causing a start of the signalCKp rising to be delayed and causing a slope of the transition to besteep.

Accordingly, the inverters IV8 to IV11 and the BT circuit BT2 functionas a generation circuit of the signal CKp.

An output terminal of the inverter IV12 is connected to an outputterminal of the inverter IV13 and an input terminal of the inverter IV14via the node NA. The inverter IV12 is a clocked inverter configured toinvert a signal DA in accordance with timings of the signals CKp andCKn. More specifically, for example, in a case where the signal CKp hasan “L” level and the signal CKn has an “H” level, the inverter IV12outputs an inversion signal of the signal DA to the node NA. Theinverter IV12 includes p channel MOS transistors P12 a and P12 b and nchannel MOS transistors N12 a and N12 b. A gate of the transistor P12 ais connected to the input terminal of the inverter IV12 and a gate ofthe transistor N12 a. A source of the transistor P12 a is connected tothe power-supply voltage terminal. A drain of the transistor P12 a isconnected to a source of the transistor P12 b. A drain of the transistorP12 b is connected to the output terminal of the inverter IV12 and adrain of the transistor N12 b. A source of the transistor N12 a isgrounded. A drain of the transistor N12 a is connected to a source ofthe transistor N12 b.

An input terminal of the inverter IV13 is connected to an outputterminal of the inverter IV14 and an input terminal of the inverter IV15via the node NB. The inverter IV13 is a clocked inverter configured toinvert data at the node NB in accordance with timings of the outputsignals of the inverters IV7 and IV11. More specifically, for example,in a case where the output signal of the inverter IV7 has an “L” level,and the output signal of the inverter IV11 has an “H” level, theinverter IV13 outputs an inversion signal at the node NB to the node NA.The inverter IV13 has a configuration similar to that of the inverterIV12, and includes transistors P13 a, P13 b, N13 a, and N13 b.

The inverter IV14 has a configuration similar to that of the inverterIV12, and includes transistors P14 a, P14 b, N14 a, and N14 b. A gate ofthe transistor P14 b is grounded. A gate of the transistor N14 b isconnected to the power-supply voltage terminal. The inverters IV13 andIV14 constitute a latch circuit, and thus inversion data of the node NAis held at the node NB.

The inverter IV15 outputs inversion data of the node NB to the outsideof the latch DIN. The inverter IV15 has a configuration similar to thatof the inverter IV1, and includes transistors P15 and N15.

1. 2 Specific Example of Operation of Latch Circuit for Data Input

Next, a specific example of an operation of the latch circuit for datainput DIN will be described with reference to FIG. 6 . In the example inFIG. 6 , a case where, when a period from an input of a signal I/O untilthe logical levels of the signals DQS and BDQS are inverted issubstantially equal to or slightly longer than the set-up period, thesignal DA is transitioned from an “L” level to an “H” level and datahaving an “L” level is latched at the node NA is shown.

At a time point t1, the latch DIN starts transition of the logical levelof the signal DA. The signal DA is transitioned from an “L” level to an“H” level.

At a time point t2, the latch DIN starts transition of the logical level(potential) of the node NA. The signal at the node NA is transitionedfrom an level to an L level. More specifically, since the signal CKp hasan “L” level and the signal CKn has an “H” level, the transistors P12 band N12 b in the inverter IV12 are an ON state. In this state, if thesignal DA is transitioned from an “L” level to an “H” level, theinverter IV12 starts discharging at the node NA when the potential ofthe signal DA exceeds the threshold voltage of the transistor N12 a.That is, a period of the time points t1 to t2 is a delay period by theinverter IV12.

At a time point t3, transition of the output signals of the invertersIV7 and IV11 is started. More specifically, the output signal of theinverter IV7 is transitioned from an “H” level to an “L” level, and theoutput signal of the inverter IV11 is transitioned from an “L” level toan “H” level.

At a time point t4, if the potential of a gate of the transistor P13 bin the inverter IV13, that is, the potential of the output signal of theinverter IV7 is decreased to a voltage which is lower than (power supplyvoltage-threshold voltage Vtp), and the potential of the gate of thetransistor N13 b in the inverter IV13, that is, the potential of theoutput signal of the inverter IV11 is increased to a voltage which ishigher than the threshold voltage Vtn, the transistors P13 b and N13 bin the inverter IV13 are in an ON state. The inverter IV13 outputs aninversion signal of the node NB, that is, a signal having an “H” level,to the node NA.

At a time point t5, the transistor N41 of the BT circuit BT1 and thetransistor P42 of the BT circuit BT2 go into an ON state. Thus, thesignal CKp is rapidly transitioned from an “L” level to an “H” level,and the signal CKn is rapidly transitioned from an “H” level to an “L”level. In the inverter IV12, the transistors P12 b and N12 b go into anOFF state in accordance with the signals CKp and CKn. Thus, dischargingat the node NA is ended. Accordingly, a period of the time points t2 tot5 is a discharging period of the node NA in the inverter IV12. At thistime, if the potential at the node NA is smaller than an inversion levelat the node NB in the inverter IV14, the potential at the node NB isinverted from an “L” level to an “H” level. Thus, the signal having an“L” level is held at the node NA, and the signal having an “H” level isheld at the node NB.

In a case where the signal DA is transitioned from an “H” level to an“L” level, the period of the time points t2 to t5 functions as thecharging period of the node NA.

1. 3 Effects According to First Embodiment

With the configuration according to the first embodiment, it is possibleto improve processing speed. The effect will be described below by usinga comparative example.

First, the comparative example will be described with reference to FIGS.7 and 8 .

FIG. 7 illustrates an example of a latch circuit for data inputaccording to the comparative example. In the example in FIG. 7 , the BTcircuits BT1 and BT2 which are described in FIG. 5 in the firstembodiment are not provided.

As illustrated in FIG. 7 , the output signal of the inverter IV11 isinput as the signal CKp, to the gate of the transistor P12 b of theinverter IV12. The output signal of the inverter IV7 is input as thesignal CKn, to the gate of the transistor N12 b. Other components arethe same as those in FIG. 5 in the first embodiment.

Next, FIG. 8 illustrates a specific example of an operation in the latchcircuit for data input, which is illustrated in FIG. 7 . In the examplein FIG. 8 , a case where the length of a period from an input of thesignal I/O until the logical levels of the signals DQS and BDQS areinverted is equal to that in FIG. 6 is shown.

As illustrated in FIG. 8 , at a time point t1, transition of the signalDA which is an inversion delay signal of the signal I/O is started. Thesignal DA is transitioned from an “L” level to an “H” level. At a timepoint t2, the signal CKp which is a signal obtained by delaying thesignal BDQS has an “L” level, and the signal CKn which is a signalobtained by delaying the signal DQS has an “H” level. Thus, dischargingat the node NA is started. Then, at a time point t3, transition of thesignal CKp and the signal CKn, that is, the output signals of theinverters IV7 and IV11, is started. After the transition has started,the transistor N12 b (and P12 b) in the inverter IV12 goes into an OFFstate at a time point t4, and discharging at the node NA is ended. Inthis case, the potential at the node NA is not decreased to a levelwhich is smaller than the inversion level at the node NB. Thus, an “H”level is continuously held at the node NA and an “L” level as inversiondata of the signal DA is not latched.

That is, in the latch circuit for data input illustrated in FIG. 7 , ina case where the length of the period from an input of the signal I/Ountil the logical levels of the signals DQS and BDQS are inverted isequal to that in FIG. 6 , a period from a transition start of the signalDA to a transition start of the signals CKp and CKn is shorter than thatin FIG. 6 . Thus, the discharging period at the node NA is reduced inthe inverter IV12. Thus, it may not be possible to properly latch thesignal DA (input signal I/O).

Accordingly, in a case using the latch circuit for data inputillustrated in FIG. 7 , it is necessary that the period from an input ofthe signal I/O until the logical levels of the signals DQS and BDQS areinverted needs to be increased (the set-up period is increased), inorder to sufficiently secure the length of the period from thetransition start of the signal DA to the transition start of the signalsCKp and CKn. Therefore, adjustment is required so as to delay the signalDQS and the signal BDQS relative to the input signal I/O. In a casewhere a new delay circuit for the signals DQS and BDQS is provided, adelay period between data (input signal I/O) and the clock (signals DQSand BDQS) depends on a circuit which is different from the latch DIN.Thus, the delay period varies depending on variation in manufacturing(process) of a semiconductor device, variation in a voltage, ordependency of an operation temperature (temperature) (referred to as“PVT dependency” below). Consequently, the set-up period/holding periodis required to be increased more. If the set-up period/holding periodbecomes longer, it is not possible to increase the speed of datareception in the input I/F. Thus, the processing speed of asemiconductor device is lowered.

On the contrary, the BT circuits BT1 and BT2 are provided in theconfiguration according to the first embodiment. Thus, it is possible toshape a waveform of the signals CKp and CKn. More specifically, in theBT circuit, it is possible to output a signal which has a delayedtransition start of the logical level and has rapid transition (changeof the potential) of the logical level (fast transition speed) incomparison to those of an input signal (for example, output signals ofthe inverters IV7 and IV11). Thus, in the inverter IV12, whendischarging (or charging) at the node NA is performed, it is possible tosecure the discharging (or charging) period for inverting the logicallevel at the node NA so as to be increased in comparison to that in acase where the BT circuit is not provided. Accordingly, it is notnecessary that the signals DQS and BDQS are unnecessarily delayedrelative to the input signal I/O. Thus, it is possible to reduce PVTdependency on the set-up period/holding period. Further, it is possibleto reduce a set-up period/holding period of the latch circuit DIN fordata input, and to increase the speed of data reception in the input I/F410. Thus, it is possible to improve the processing speed of asemiconductor device.

2. Second Embodiment

Next, a semiconductor device according to a second embodiment will bedescribed. In the second embodiment, a configuration of a latch circuitfor data input DIN which is different from that in the first embodimentwill be described. Only points which are different from that in thefirst embodiment will be described below.

2. 1 Configuration of Latch Circuit for Data Input

A configuration of the latch circuit DIN for data input will bedescribed with reference to FIG. 9 .

As illustrated in FIG. 9 , the latch DIN includes inverters IV1, IV2,IV4, IV5, IV8, IV9, and IV12 to IV20, and delay circuits DL1 and DL2.The configuration of the inverters IV1, IV2, IV4, IV5, IV8, IV9, andIV12 to IV15 is the same as that in FIG. 5 in the first embodiment. InFIG. 9 , the BT circuits BT1 and BT2 which are described with referenceto FIG. 5 are removed. In FIG. 9 , the inverters IV16 to IV20 having aconfiguration which is the same as that of the inverter IV14 are usedinstead of the inverters IV3, IV6, IV7, IV10, and IV11 illustrated inFIG. 5 in the first embodiment. However, similarly to the firstembodiment, the inverters IV3, IV6, IV7, IV10, and IV11 may be used.

An output terminal of the delay circuit DL1 is connected to the gate ofthe transistor P13 b in the inverter IV13. A signal (referred to as “asignal CKn_dly” below) obtained by delaying the signal DQS through theinverters IV4, IV5, and IV17 and the delay circuit DL1 is input to thegate of the transistor P13 b. An output terminal of the delay circuitDL2 is connected to the gate of the transistor N13 b. A signal (referredto as “a signal CKp_dly” below) obtained by delaying the signal BDQSthrough the inverters IV8, IV9, and IV19 and the delay circuit DL2 isinput to the gate of the transistor N13 b. The signals CKn_dly andCKp_dly are signals obtained in a manner that the signals CKn and CKpare delayed by two stages of the inverter.

An input terminal of the inverter IV16 is connected to the outputterminal of the inverter IV2. An output terminal of the inverter IV16 isconnected to an input terminal of the inverter IV12. The inverter IV16has a configuration similar to that of the inverter IV14, and includestransistors P16 a, P16 b, N16 a, and N16 b.

An input terminal of the inverter IV17 is connected to the outputterminal of the inverter IV5. An output terminal of the inverter IV17 isconnected to an input terminal of the inverter IV18 and an inputterminal of the delay circuit DL1. The inverter IV17 has a configurationsimilar to that of the inverter IV14, and includes transistors P17 a,P17 b, N17 a, and N17 b.

An output terminal of the inverter IV18 is connected to the gate of thetransistor N12 b in the inverter IV12. The inverter IV18 has aconfiguration similar to that of the inverter IV14, and includestransistors P18 a, P18 b, N18 a, and N18 b.

An input terminal of the inverter IV19 is connected to an outputterminal of the inverter IV9. An output terminal of the inverter IV19 isconnected to an input terminal of the inverter IV20 and an inputterminal of the delay circuit DL2. The inverter IV19 has a configurationsimilar to that of the inverter IV14, and includes transistors P19 a,P19 b, N19 a, and N19 b.

An output terminal of the inverter IV20 is connected to the gate of thetransistor P12 b in the inverter IV12. The inverter IV20 has aconfiguration similar to that of the inverter IV14, and includestransistors P20 a, P20 b, N20 a, and N20 b.

The delay circuit DL1 includes inverters IV21 to IV23. The invertersIV21 to IV23 are connected in series. An input terminal of the inverterIV21 is connected to the input terminal of the delay circuit DL1. Anoutput terminal of the inverter IV23 is connected to an output terminalof the delay circuit DL1. The inverters IV21 to IV23 have aconfiguration similar to that of the inverter IV1. The inverter IV21includes transistors P21 and N21. The inverter IV22 includes transistorsP22 and N22. The inverter IV23 includes transistors P23 and N23.

Although the three inverters IV21 to IV23 are connected in series, thenumber of inverters which are connected in series may be changed so longas the logical level is not inverted. It is necessary that the signalCKn_dly is delayed relative to the signal CKn. Thus, the number ofinverters may be any odd number which is equal to or greater than three.Further, in the second embodiment, the input terminal of the inverterIV21 is connected to the output terminal of the inverter IV17. However,the input terminal of the inverter IV21 may be connected to the outputterminal of the inverter IV18. In this case, the number of inverters inthe delay circuit DL1 may be any even number which is equal to orgreater than two (for example, inverters IV21 and IV22), such that thelogical level is not inverted.

The delay circuit DL2 includes inverters IV24 to IV26. The invertersIV24 to IV26 are connected in series. An input terminal of the inverterIV24 is connected to an input terminal of the delay circuit DL2. Anoutput terminal of the inverter IV26 is connected to an output terminalof the delay circuit DL2. The inverters IV24 to IV26 have aconfiguration similar to that of the inverter IV1. The inverter IV24includes transistors P24 and N24. The inverter IV25 includes transistorsP25 and N25. The inverter IV26 includes transistors P26 and N26.Although three inverters IV24 to IV26 are connected in series, thenumber of inverters which are connected in series may be any numberequal to the number of inverters in the delay circuit DL1.

2. 2 Specific Example of Operation of Latch Circuit for Data Input

Next, a specific example of an operation of the latch circuit DIN fordata input DIN will be described with reference to FIG. 10 . In theexample in FIG. 10 , a case where data having an “L” level is latched atthe node NA in a state where a period from an input of a signal I/Ountil the logical levels of the signals DQS and BDQS are inverted issubstantially equal to or slightly longer than the set-up period isshown.

At a time point t1, the latch DIN starts transition of the logical levelof the signal DA. The signal DA is transitioned from an “L” level to an“H” level.

At a time point t2, the latch DIN starts transition of the logical levelat the node NA. The signal at the node NA is transitioned from an “H”level to an “L” level.

At a time point t3, transition of the logical levels of the signals CKpand CKn is started. More specifically, the signal CKp is transitionedfrom an “L” level to an “H” level, and the signal CKn is transitionedfrom an “H” level to an L level. If the potential at the node NA issmaller than an inversion level at the node NB, the inverter IV14increases the potential at the node NB.

At a time point t4, the transistor N12 b (and P12 b) in the inverterIV12 goes into an OFF state, and discharging at the node NA is ended.Accordingly, a period of the time points t2 to t4 is a dischargingperiod of the node NA in the inverter IV12.

At a time point t5, transition of the signals CKp_dly and CKn_dly isstarted. More specifically, the signal CKp_dly is transitioned from an“L” level to an “H” level, and the signal CKn_dly is transitioned froman “H” level to an “L” level. Accordingly, a period of the time pointst3 to t5 is a delay period by the delay circuits DL1 and DL2.

At a time point t6, the transistors P13 b and N13 b of the inverter IV13go into an ON state. Thus, the inverter IV13 outputs an inversion signalat the node NB, to the node NA. Accordingly, at the time point t6, thelogical level of the latch circuit configured with the inverters IV13and IV14 is determined. That is, since the signals CKp_dly and CKn_dlyare respectively delayed relative to the signals CKp and CKn, it ispossible to secure a sufficient period for increasing the potential atthe node NB up to an “H” level. As a result, a signal having an “L”level is held at the node NA and a signal having an “H” level is held atthe node NB.

2. 3 Effects According to Second Embodiment

With the configuration according to the second embodiment, it ispossible to obtain an effect which is similar to that in the firstembodiment. The effect will be described below by using a comparativeexample.

First, the comparative example will be described with reference to FIG.11 . In the example in FIG. 11 , a specific example of an operation inthe comparative example of the latch for data input illustrated in FIG.7 is illustrated. The example in FIG. 11 shows a case where the lengthof the period from an input of the signal I/O until the logical levelsof the signals DQS and BDQS are inverted is equal to that in FIG. 10 .

As illustrated in FIG. 11 , at a time point t1, transition of thelogical level of the signal DA is started, and the signal DA istransitioned from an “L” level to an “H” level. After the transition hasstarted, at a time point t2, the signal CKp has an “L” level and thesignal CKn has an “H” level. Thus, discharging at the node NA isstarted. Then, at a time point t3, transition of the signal CKp and thesignal CKn is started. After the transition has started, at a time pointt4, the transistor N12 b (and P12 b) in the inverter IV12 goes into anOFF state, and discharging at the node NA is ended. The transistors N13b and P13 b in the inverter IV13 go into an ON state. That is, the latchcircuit configured with the inverters IV13 and IV14 is in a chargeholding state. The inverter IV12 ends discharging at the node NA in astate where the level at the node NA is slightly lower than an inversionlevel at the node NB. The latch circuit configured with the invertersIV13 and IV14 is switched to the charge holding state. If the switchingis performed, the potential at the node NB at the time point t4 is an“L” level (not increased up to an “H” level). Thus, the latch circuitoperates so as to cause the potential at the node NA to be brought backto the “H” level again. Thus, the signal at the node NA is not invertedto an “L” level.

That is, in the latch circuit for data input illustrated in FIG. 7 , anend of discharging at the node NA in the inverter IV12 (timing when thetransistors N12 b and P12 b go into an OFF state) is performed at thesubstantially same timing as a timing when the inverter IV13 transitionsto the charge holding state (timing when the transistors N13 b and P13 bgo into an OFF state). Therefore, in a case where the length of theperiod from an input of the signal I/O until the logical levels of thesignals DQS and BDQS are inverted is equal to that in FIG. 10 , in thelatch circuit for data input illustrated in FIG. 7 , it is not possibleto transition the logical level at the node NB by the inverter IV14.Thus, it may not be possible to properly latch the signal DA (inputsignal I/O).

Thus, in a case of using the latch for data input illustrated in FIG. 7, it is necessary that the set-up period/holding period is increased, inorder to secure a transition period at the node NB. If the signals DQSand BDQS are delayed more in order to optimize the set-up period/holdingperiod, the delay period varies by PVT dependency. Thus, it is necessarythat the set-up period/holding period is increased more. If the set-upperiod/holding period becomes longer, it is not possible to increase thespeed of data reception in the input I/F. Thus, the processing speed ofa semiconductor device is lowered.

On the contrary, the delay circuits DL1 and DL2 are provided in theconfiguration according to the third embodiment. Thus, it is possible todelay the signals CKp_dly and CKn_dly input to the inverter IV13,relative to the signals CKp and CKn input to the inverter IV12. Thus,even in a case where the inverter IV12 ends discharging at the node NAin a state where the potential at the node NA is slightly lower than aninversion level at the node NB, it is possible to increase the potentialat the node NB up to an “H” level during the delay period of the signalsCKp_dly and CKn_dly. In addition, it is possible to invert the logicallevel at the node NA. Thus, it is possible to determine the set-upperiod/holding period only by using an input of the signal DA to theinverter IV12 and a timing of the signals CKp and CKn. Since adjustmentof the delay period the signal DQS and the signal BDQS, it is possibleto reduce the PVT dependency of the set-up period/holding period.Further, it is possible to reduce the set-up period/holding period ofthe latch circuit DIN for data input, and to increase the speed of datareception in the input I/F 410. Thus, it is possible to improve theprocessing speed of a semiconductor device.

3. Third Embodiment

Next, a semiconductor device according to a third embodiment will bedescribed. In the third embodiment, a configuration of a latch circuitDIN for data input, which is different from the first and secondembodiments will be described. Only points which are different from thatin the first and second embodiments will be described below.

3. 1 Configuration of Latch Circuit for Data Input

The configuration of the latch circuit DIN for data input will bedescribed with reference to FIG. 12 .

As illustrated in FIG. 12 , the latch DIN includes inverters IV2, IV4,IV8, and IV12 to IV20, an inverter IV27, and a correction circuit CR(inverters IV28 to IV31). The configuration of the inverters IV2, IV4,IV8, and IV12 to IV20 is the same as that in FIG. 5 in the firstembodiment and FIG. 9 in the second embodiment. In FIG. 12 , the BTcircuits BT1 and BT2 which are described with reference to FIG. 5 , andthe delay circuits DL1 and DL2 which are described with reference toFIG. 9 are not present.

An output terminal of the inverter IV18 is connected to the transistorN12 b of the inverter IV12 and the transistor P13 b of the inverterIV13. That is, the signal CKn is input to the gate of the transistor N12b and the gate of the transistor P13 b.

An output terminal of the inverter IV20 is connected to the transistorP12 b in the inverter IV12 and the transistor N13 b in the inverterIV13. That is, the signal CKp is input to the gate of the transistor P12b and the gate of the transistor N13 b.

The input signal I/O is input to an input terminal of the inverter IV27.An output terminal of the inverter IV27 is connected to the inputterminal of the inverter IV2. The inverter IV27 includes p-channel MOStransistors P27 a to P27 c and N-channel MOS transistors N27 a to N27 c.A gate of the transistor P27 a is connected to the input terminal of theinverter IV27 and a gate of each of the transistors P27 b, P27 c, andN27 a to N27 c. A source of the transistor P27 a is connected to thepower-supply voltage terminal. A drain of the transistor P27 a isconnected to the output terminal of the inverter IV27 and a drain ofeach of the transistors P27 c, N27 a, and N27 c. A source of thetransistor N27 a is grounded. A source of the transistor P27 b isconnected to the power-supply voltage terminal, and a drain of thetransistor P27 b is connected to a source of the transistor P27 c. Asource of the transistor N27 b is grounded, and a drain of thetransistor N27 b is connected to a source of the transistor N27 c. Theinverter IV27 also represents two inverters: an inverter includingtransistors P27 a and N27 a and an inverter including transistors P27 b,P27 c, N27 b, and N27 c. The inverter IN27 has a configuration similarto that of the inverters IV28 and IV30 so that an amount of delay fromthe input signal introduced by them can be made equal.

The correction circuit CR corrects variation of a duty ratio in thesignals DQS and BDQS, that is, a difference (simply referred to as “anHL difference” below) of the length between a period of an “L” level anda period of an “H” level in the clock signal. The HL difference occursin, for example, the input receiver IR. If the HL difference occurs, atiming when the logical level of the signal DQS is inverted is shiftedfrom a timing when the logical level of the signal BDQS is inverted. Ifthe HL difference is corrected by using the correction circuit CR andvariation in timings of the signals CKp and CKn is reduced, for example,variation in the length of the transition period of the potential(logical level) at the node NA is reduced.

The correction circuit CR includes inverters IV28 to IV31. An inputterminal of the inverter IV28 is connected to the output terminal of theinverter IV4 and an input terminal of the inverter IV29. An outputterminal of the inverter IV28 is connected to the input terminal of theinverter IV17. A clock signal based on the signal DQS output from theinverter IV28 to the inverter IV17 is referred to as “DM” below. Theinverter IV28 has a configuration similar to that of the inverter IV27,and includes transistors P28 a to P28 c and N28 a to N28 c. A gate ofeach of the transistors P28 a, P28 b, N28 a, and N28 b is connected tothe input terminal of the inverter IV28. A gate of the transistor P28 cis connected to an output terminal of the inverter IV29 and a gate ofthe transistor P30 c in the inverter IV30. A gate of the transistor N28c is connected to an output terminal of the inverter IV31 and a gate ofthe transistor N30 c in the inverter IV30.

The inverter IV29 has a configuration similar to that of the inverterIV1, and includes transistors P29 and N29.

An input terminal of the inverter IV30 is connected to the outputterminal of the inverter IV8 and an input terminal of the inverter IV31.An output terminal of the inverter IV30 is connected to the inputterminal of the inverter IV19. A clock signal based on the signal BDQSoutput from the inverter IV30 to the inverter IV19 is referred to as“BM” below. The inverter IV30 has a configuration similar to that of theinverter IV28, and includes transistors P30 a to P30 c and N30 a to N30c. A gate of each of the transistors P30 a, P30 b, N30 a, and N30 b isconnected to an input terminal of the inverter IV30.

The inverter IV31 has a configuration similar to that of the inverterIV1, and includes transistors P31 and N31.

In the example in FIG. 12 , the correction circuit CR that corrects asignal corresponding to the signal BDQS in a case where a period of an“L” level is shorter than a period of an “H” level is described.However, it is not limited thereto. For example, a correction circuit inwhich the connection of the output terminal of the inverter IV29 and theconnection of the output terminal of the inverter IV31 are swapped and asignal corresponding to the signal DQS is corrected, may be provided. Inaddition, a correction circuit in which the position of the correctioncircuit CR and the position of the inverters IV17 and IV19 are swapped,and a signal is corrected in a case where a period of an “H” level isshorter than a period of an “L” level, may be provided. The correctioncircuit CR may be changed to any of the above correction circuits. Aplurality of correction circuits may also be provided.

3. 2 Specific Example of Operation of Correction Circuit

Next, a specific example of an operation of the correction circuit CRwill be described.

3. 2. 1 Case where Period of “L” level is Short

First, a case where a period of an L level is shorter than a period ofan “H” level will be described with reference to FIG. 13 .

As illustrated in FIG. 13 , at a time point t1, the signal DQS istransitioned from an “L” level to an “H” level.

At a time point t2, the signal BDQS is transitioned from an “H” level toan “L” level. A period of the time points t1 to t2 corresponds to the HLdifference.

At a time point t3, the correction circuit CR causes the signal DM to betransitioned from an “L” level to an “H” level. More specifically, theoutput signal of the inverter IV4 (inversion signal (“L” level) of thesignal DQS) is input to the inverters IV28 and IV29. Thus, in theinverter IV28, the transistors P28 a and P28 b go into an ON state andthe transistors N28 a and N28 b go into an OFF state. Since the inverterIV29 outputs a signal of an “H” level, the transistor P28 c is in an OFFstate. Further, since the inverter IV31 outputs a signal of an “H”level, the transistor N28 c is in an ON state. Thus, an output of theinverter IV28 has an “H” level via the transistor P28 a.

At a time point t4, the correction circuit CR causes the signal BM to betransitioned from an “H” level to an “L” level. More specifically, theoutput signal of the inverter IV8 (inversion signal (“H” level) of thesignal BDQS) is input to the inverters IV30 and IV31. Thus, in theinverter IV30, the transistors P30 a and P30 b go into an OFF state andthe transistors N30 a and N30 b go into an ON state. Since the inverterIV31 outputs a signal of an “L” level, the transistor N30 c is in an OFFstate. Further, since the inverter IV29 outputs a signal of an “H” levelat the time point t3, the transistor P30 c is in an OFF state. Thus, anoutput of the inverter IV30 has an “L” level via the transistor N30 a.

At this time, since the transistor P30 c goes into an OFF state at thetime point t3, it can be considered that the inverter IV30 is configuredwith the transistors P30 a and N30 a to N30 c. Therefore, a β ratio ofthe inverter IV30, that is, a ratio of β in the n-channel MOS transistorand in the p-channel MOS transistor is changed. As a result, the dutyratio varies and a period of an “L” level in the signal BM becomeslonger than that in the signal BDQS. Further, since the load of the pchannel MOS transistor is reduced, the delay period by the inverter IV30is reduced. Thus, a timing of the transition start of the signal BMbecomes earlier than that in a case where the β ratio of the inverterIV30 is not changed.

At a time point t5, the signal BDQS is transitioned from an “L” level toan “H” level. A period of the time points t2 to t5 when the signal BDQShas an “L” level is described as “a period tL_BDQS” below.

At a time point t6, the signal DQS is transitioned from an “H” level toan “L” level. A period of the time points t1 to t6 when the signal DQShas an “H” level is described as “a period tH_DQS” below.

At a time point t7, the correction circuit CR causes the signal BM to betransitioned from an “L” level to an “H” level. More specifically, theoutput signal of the inverter IV8 (inversion signal (“L” level) of thesignal BDQS) is input to the inverters IV30 and IV31. Thus, in theinverter IV30, the transistors P30 a and P30 b go into an ON state andthe transistors N30 a and N30 b go into an OFF state. Since the inverterIV31 outputs a signal of an “H” level, the transistor N30 c is in an ONstate. Further, since the inverter IV29 outputs a signal of an “H”level, the transistor P30 c is in an OFF state. Thus, an output of theinverter IV30 has an “H” level via the transistor P30 a.

At this time, in the inverter IV30, similar to a case of the time pointt4, a timing when the signal BM is transitioned form an “L” level to an“H” level is delayed by the change of the ratio, in comparison to thatin a case where the ratio of the inverter IV30 is not changed.

Thus, a period (period tL_BM) of the time point t4 to the time point t7when the signal BM has an “L” level becomes longer than the periodtL_BDQS. Accordingly, the HL difference in the signal CKp is reduced.

At a time point t8, the correction circuit CR causes the signal DM to betransitioned from an “H” level to an “L” level. More specifically, theoutput signal of the inverter IV4 (inversion signal (“H” level) of thesignal DQS) is input to the inverters IV28 and IV29. Thus, in theinverter IV28, the transistors P28 a and P28 b go into an OFF state andthe transistors N28 a and N28 b go into an ON state. Since the inverterIV29 outputs a signal of an “L” level, the transistor P28 c is in an ONstate. Further, since the inverter IV31 outputs a signal of an “H”level, the transistor N28 c is in an ON state. Thus, an output of theinverter IV28 has an “L” level via the transistors N28 a to N28 c. Aperiod (period tH_DM) of the time point t3 to the time point t8 when thesignal DM has an “H” level has substantially the same as that of theperiod tH_DQS.

3. 2. 2 Case where Period of “H” Level is Short

Next, a case where a period of an “H” level is shorter than a period ofan “L” level will be described with reference to FIG. 14 .

As illustrated in FIG. 14 , at a time point t1, the signal BDQS istransitioned from an level to an “L” level.

At a time point t2, the signal DQS is transitioned from an “L” level toan “H” level. A period of the time points t1 to t2 corresponds to the HLdifference.

At a time point t3, the correction circuit CR causes the signal BM to betransitioned from an “H” level to an “L” level. More specifically, theoutput signal of the inverter IV8 (inversion signal (“H” level) of thesignal BDQS) is input to the inverters IV30 and IV31. Thus, in theinverter IV30, the transistors P30 a and P30 b go into an OFF state andthe transistors N30 a and N30 b go into an ON state. Since the inverterIV31 outputs a signal of an “L” level, the transistor N30 c is in an OFFstate. Further, since the transistor IV29 outputs a signal of an “L”level, the transistor P30 c is in an ON state. Thus, an output of theinverter IV30 has an “H” level via the transistor N30 a.

At a time point t4, the correction circuit CR causes the signal DM to betransitioned from an “L” level to an “H” level. More specifically, theoutput signal of the inverter IV4 (inversion signal (“L” level) of thesignal DQS) is input to the inverters IV28 and IV29. Thus, in theinverter IV28, the transistors P28 a and P28 b go into an ON state andthe transistors N28 a and N28 b go into an OFF state. Since the inverterIV29 outputs a signal of an “H” level, the transistor P28 c is in an OFFstate. Further, since the inverter IV31 outputs a signal of an “L”level, the transistor N28 c is in an OFF state. Thus, the output of theinverter IV28 has an “H” level via the transistor P28 a.

At a time point t5, the signal DQS is transitioned from an “H” level toan “L” level. A period of the time points t2 to t5 corresponds to theperiod tH_DQS.

At a time point t6, the signal BDQS is transitioned from an “L” level toan “H” level. A period of the time points t1 to t6 corresponds to theperiod tL_BDQS.

At a time point t7, the correction circuit CR causes the signal DM to betransitioned from an “H” level to an “L” level. More specifically, theoutput signal of the inverter IV4 (inversion signal (“H” level) of thesignal DQS) is input to the inverters IV28 and IV29. Thus, in theinverter IV28, the transistors P28 a and P28 b go into an OFF state andthe transistors N28 a and N28 b go into an ON state. Since the inverterIV29 outputs a signal of an “L” level, the transistor P28 c is in an ONstate. Further, since the inverter IV31 outputs a signal of an “L”level, the transistor N28 c is in an OFF state. Thus, the output of theinverter IV28 has an “L” level via the transistor N28 a. At this time, aperiod of the time point t4 to the time point t7, that is, the periodtH_DM has a length which is substantially the same as that of the periodtH_DQS.

At a time point t8, the correction circuit CR causes the signal BM to betransitioned from an “L” level to an “H” level. More specifically, theoutput signal of the inverter IV8 (inversion signal (“L” level) of thesignal BDQS) is input to the inverters IV30 and IV31. Thus, in theinverter IV30, the transistors P30 a and P30 b go into an ON state andthe transistors N30 a and N30 b go into an OFF state. Since the inverterIV31 outputs a signal of an “H” level, the transistor N30 c is in an ONstate. Further, since the transistor IV29 outputs a signal of an “L”level, the transistor P30 c is in an ON state. Thus, the output of theinverter IV30 has an “H” level via the transistors P30 a to P30 b. Atthis time, a period of the time point t3 to the time point t8, that is,the period tL_BM has a length which is substantially the same as that ofthe period tL_BDQS.

Thus, the correction circuit CR according to the third embodiment doesnot correct the HL difference in a case where the period of an “H” levelis short.

However, in a case where the period of an “H” level is short, adifferent correction circuit for correcting the HL difference may befurther provided. As noted above, in such a correction circuit, theposition of the correction circuit CR and the position of the invertersIV17 and IV19 are swapped.

3. 3 Effects According to Third Embodiment

With the configuration according to the third embodiment, it is possibleto obtain an effect which is similar to that in the first and secondembodiments. The effect will be described below.

First, an influence of the HL difference on the latch DIN will bedescribed with reference to FIGS. 15 and 16 . In the example in FIG. 15, an example of the signals DA, CKp, and CKn and the potential at thenode NA in a case where the period of an “L” level is short isdescribed. In the example in FIG. 16 , an example of the signals DA,CKp, and CKn and the potential at the node NA in a case where the periodof an “H” level is short is described.

As illustrated in FIG. 15 , in a case where the period of an “L” levelis short, for example, at a time point t1, the signal CKp istransitioned from an “L” level to an “H” level. At this time, since thesignals CKp and CKn have an “H” level, the transistor P12 b in theinverter IV12 goes into an OFF state and the transistor N12 b goes intoan ON state. At a time point t2, the signal DA is transitioned from an“L” level to an “H” level. At this time, since the transistor P12 b isin an OFF state, an influence of a capacitive load by the p-channel MOStransistor on an operation of the inverter IV12 is relatively small.Thus, it can be considered that the inverter IV12 is driven only by thetransistors N12 a and N12 b. Thus, the signal at the node NA isdischarged more rapidly than in a case where the HL difference does notoccur. That is, the transition speed at the node NA becomes faster.

As illustrated in FIG. 16 , in a case where the period of an “H” levelis short, for example, at a time point t1, the signal DA is transitionedfrom an “L” level to an “H” level. At this time, the signal CKp has an“L” level and the signal CKn has an “H” level. Thus, the transistors P12b and N12 b in the inverter IV12 are in an ON state. Thus, the influenceof the capacitive load by the p-channel MOS transistor on the operationof the inverter IV12 is increased in comparison to that in the examplein FIG. 15 . Thus, the transition speed at the node NA becomes slowerthan that in the example in FIG. 15 .

At a time point t2, if the signal CKn is transitioned from an “H” levelto an “L” level, the transistor N12 b goes into an OFF state. Therefore,discharging at the node NA is ended. At this time, the inverter IV12ends discharging at the node NA in a state where the level at the nodeNA is slightly lower than an inversion level at the node NB. If thedischarging is ended, the potential at the node NB has an “L” level (instate of being not increased up to an “H” level). Thus, the transistorP13 a in the inverter IV13 goes into an ON state. Further, since thesignal CKn has an L level, the transistor P13 b also goes into an ONstate. Thus, since the inverter IV13 charges the potential at the nodeNA, the potential at the node NA is brought back to an “H” level. At atime point t3, if the signal CKp is transitioned from an “L” level to an“H” level, the transistor N13 b in the inverter IV13 goes into an ONstate and the logical level at the node NA is determined to be an “H”level. If the period of an “H” level is reduced, it is not possible tosufficiently secure a discharging period at the node NA and it may benot possible to latch an inversion signal of the signal DA.

Thus, in a case where HL difference between the signals DQS and BDQS(signals CKn and CKp) occurs, an operation timing of the p-channel MOStransistor is shifted from an operation timing of the n-channel MOStransistor (time difference occurs) in the inverter IV12. Variation in acharging or discharging speed at the node NA occurs. Thus, it may not bepossible to properly latch the signal DA (input signal I/O). Thus, it isnecessary that the set-up period/holding period is set in considerationof the HL difference, and the set-up period/holding period tends tobecome longer. If the set-up period/holding period becomes longer, it isnot possible to increase the speed of data reception in the input I/F.Thus, the processing speed of a semiconductor device is lowered.

However, the correction circuit CR according to the third embodiment maybe added to the configuration, so that it is possible to reduce the HLdifference (correct the duty ratio) by the correction circuit CR. Forexample, in a case where the period of an “L” level is short, it ispossible to delay a transition start time when the signal CKp istransitioned from an “L” level to an level. Thus, it is possible toreduce variation in the transition speed at the node NA. Accordingly,since the influence of the HL difference is reduced, it is possible toreduce the set-up period/holding period of the latch circuit DIN fordata input, and to increase the speed of data reception in the input I/F410. Thus, it is possible to improve the processing speed of asemiconductor device.

4. Fourth Embodiment

Next, a semiconductor device according to a fourth embodiment will bedescribed. In the fourth embodiment, a configuration of a latch circuitDIN for data input, which is obtained by combining the components in thefirst to the third embodiments will be described. Only points which aredifferent from that in the first to third embodiments will be describedbelow.

4. 1 Configuration of Latch Circuit for Data Input

The configuration of the latch circuit DIN for data input will bedescribed with reference to FIG. 17 .

As illustrated in FIG. 17 , the latch DIN includes the inverters IV2 toIV4, IV6 to IV8, and IV10 to IV15, the BT circuits BT1 and BT2, thedelay circuits DL1 and DL2, and the correction circuit CR. Theconfigurations of each of the inverters, the BT circuits BT1 and BT2,the delay circuits DL1 and DL2, and the correction circuit CR1 are thesame as those in the first to the third embodiments.

The inverters IV27, IV2, and IV3 are connected in series. The inputsignal I/O is input to the input terminal of the inverter IV27. Theoutput terminal of the inverter IV3 is connected to the input terminalof the inverter IV12. An inversion signal DA of the input signal I/O,which is delayed by the inverters IV27, IV2, and IV3 is input to theinverter IV12.

The signal DQS is input to the input terminal of the inverter IV4. Theoutput terminal of the inverter IV4 is connected to the input terminalsof the inverters IV28 and IV29 in the correction circuit CR.

The signal BDQS is input to the input terminal of the inverter IV8. Theoutput terminal of the inverter IV8 is connected to the input terminalsof the inverters IV30 and IV31 in the correction circuit CR.

The output terminal of the inverter IV28 in the correction circuit CR isconnected to the input terminal of the inverter IV6. The output terminalof the inverter IV30 is connected to the input terminal of the inverterIV10.

The output terminal of the inverter IV6 is connected to the inputterminal of the inverter IV7, the gate of the transistor P41 in the BTcircuit BT1, and the input terminal of the delay circuit DL1.

The output terminal of the inverter IV7 is connected to one end of acurrent path of the transistor N41 in the BT circuit BT1.

The gate of the transistor N41 in the BT circuit BT1 is connected to thepower-supply voltage terminal. The other end of the current path isconnected to the drain of the transistor P41 and the gate of then-channel MOS transistor N12 b in the inverter IV12. A source of thetransistor P41 is connected to the power-supply voltage terminal.

The output terminal of the inverter IV10 is connected to the inputterminal of the inverter IV11, the gate of the transistor N42 in the BTcircuit BT2, and the input terminal of the delay circuit DL2.

The output terminal of the inverter IV11 is connected to one end of acurrent path of the transistor P42 in the BT circuit BT2.

The gate of the transistor P42 in the BT circuit BT2 is grounded. Theother end of the current path is connected to the drain of thetransistor N42 and the gate of the p-channel MOS transistor P12 b in theinverter IV12. The source of the transistor N42 is grounded.

The output terminal of the delay circuit DL1 is connected to the gate ofthe transistor P13 b in the inverter IV13. The output terminal of thedelay circuit DL2 is connected to the gate of the transistor N13 b inthe inverter IV13.

An output terminal of the inverter IV12 is connected to an outputterminal of the inverter IV13 and an input terminal of the inverter IV14via the node NA.

An input terminal of the inverter IV13 is connected to an outputterminal of the inverter IV14 and an input terminal of the inverter IV15via the node NB.

The inverter IV15 outputs inversion data of the node NB to outside ofthe latch DIN.

4. 2 Effects According to Fourth Embodiment

With the configuration according to the fourth embodiment, it ispossible to obtain an effect which is similar to that in the first tothird embodiments. It is possible to reduce the set-up period/holdingperiod of the latch circuit DIN for data input and to increase the speedof data reception in the input I/F 410, by combining the components inthe first to the third embodiments. Thus, it is possible to improve theprocessing speed of a semiconductor device.

5. Modification Example

The semiconductor device according to the above embodiments includes theinput receiver (IR in FIG. 4 ) and the latch circuit for data input (DINin FIG. 4 ) connected to the input receiver. The latch circuit for datainput includes the first inverter (IV3 in FIG. 5 ), the second inverter(IV7 in FIG. 5 ), the third inverter (IV11 in FIG. 5 ), the first clockgeneration circuit (BT1 in FIG. 5 ), the second clock generation circuit(BT2 in FIG. 5 ), the fourth inverter (IV12 in FIG. 5 ), and the latchcircuit (IV13 and IV14 in FIG. 5 ). The first inverter outputs the firstsignal (DA in FIG. 5 ) based on the input signal (I/O in FIG. 5 )received from the input receiver. The second inverter outputs a firstclock signal based on the first strobe signal (DQS in FIG. 5 ). Thethird inverter outputs a second clock signal based on the second strobesignal (BDQS in FIG. 5 ) which is an inversion signal of the firststrobe signal. The first clock generation circuit is connected to theoutput terminal of the second inverter and generates the third clocksignal (CKn in FIG. 5 ) having a transition start which is delayedrelative to the transition start of the logical level of the first clocksignal and having a transition speed faster than the transition speed ofthe logical level of the first clock signal. The second clock generationcircuit is connected to the output terminal of the third inverter andgenerates the fourth clock signal (CKp in FIG. 5 ) having a transitionstart which is delayed relative to a transition start of the logicallevel of the second clock signal and having a transition speed fasterthan a transition speed of the logical level of the second clock signal.The fourth inverter outputs an inversion signal of the first signal inaccordance with the third and fourth clock signals. The latch circuitlatches the output signal of the fourth inverter in accordance with thethird and fourth clock signals.

It is possible to provide a semiconductor device which can improveprocessing speed, by applying the above embodiments.

The embodiments are not limited to the form described above. Variousmodifications can be made.

For example, in the embodiment, the components as many as possible canbe combined.

Further, the semiconductor device in the above embodiments is notlimited to a memory system which includes a NAND flash memory. The corechip may include a memory other than the NAND flash memory.

Further, a circuit other than the inverter may be used in the delaycircuits DL1 and DL2 in the above embodiments.

In addition, “connection” in the above embodiments also includes a statewhere the components are indirectly connected with an object (forexample, a transistor, a resistor, or the like) being interposed betweenthe components.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A device comprising: a first clock generationcircuit that includes a first inverter having an input to receive afirst input clock signal, and an output to provide a first invertedclock signal having an opposite phase of the first input clock signal, afirst transistor having a gate connected to the input of the firstinverter, the first transistor connected between i) a node and ii) aconductor providing a reference voltage, and a second transistorconnected between the output of the first inverter and the node; and aclocked inverter having a first clock input connected to the node, theclocked inverter configured to generate an inversion signal having anopposite phase of an input signal, based on a signal at the node.
 2. Thedevice of claim 1, wherein a gate of the second transistor is connectedto the conductor.
 3. The device of claim 1, wherein the first transistoris a transistor of a first type, and the second transistor is atransistor of a second type.
 4. The device of claim 1, furthercomprising: a latch circuit connected to the clocked inverter andconfigured to latch the inversion signal according to the first invertedclock signal.
 5. The device of claim 1, wherein the first clockgeneration circuit is configured to: generate the signal at the nodefrom the first inverted clock signal based on a level of the first inputclock signal, wherein in response to the first input clock signalreaching a threshold level from a first level, the signal at the nodetransitions from a second level to a third level at a first rate,wherein the third level is between the first level and the second level,and as the first input clock signal reaches the second level from thethreshold level, the signal at the node transitions from the third levelto the first level at a second rate that is less than the first rate. 6.The device of claim 5, wherein the first clock generation circuit isconfigured to maintain the signal at the node to be at the second level,while the first input clock signal transitions from the first level tothe threshold level.
 7. The device of claim 1, further comprising: asecond clock generation circuit that includes a second inverter havingan input to receive a second input clock signal, and an output toprovide a second inverted clock signal having an opposite phase of thesecond input clock signal, a third transistor having a gate connected tothe input of the second inverter, the third transistor connected betweeni) another node and ii) another conductor providing another referencevoltage, and a fourth transistor connected between the output of thesecond inverter and the another node, wherein the clocked inverter has asecond clock input connected to the another node, the clock inverterconfigured to generate the inversion signal, further based on anothersignal at the another node.
 8. The device of claim 7, wherein a gate ofthe second transistor is connected to the conductor, and a gate of thefourth transistor is connected to the another conductor.
 9. The deviceof claim 7, wherein the first transistor and the fourth transistor aretransistors of a first type, and the second transistor and the thirdtransistor are transistors of a second type.
 10. The device of claim 7,further comprising: a latch circuit connected to the clocked inverterand configured to latch the inversion signal according to the firstinverted clock signal and the second inverted clock signal.
 11. A devicecomprising: a first clock generation circuit configured to: receive afirst input clock signal transitioning from a first level to a secondlevel, and generate a first modified clock signal transitioning from thesecond level to a third level that is between the first level and thesecond level at a first rate, in response to the first input clocksignal reaching a threshold level from the first level, and from thethird level to the first level at a second rate less than the firstrate, as the first input clock signal reaches the second level from thethreshold level; a clocked inverter configured to generate an inversionsignal having an opposite phase of an input signal, based on the firstmodified clock signal having a voltage between the third level and thesecond level; and a latch circuit configured to latch the inversionsignal from the clock inverter.
 12. The device of claim 11, wherein thefirst clock generation circuit further includes: a first inverterconfigured to generate a first inverted clock signal having an oppositephase of the first input clock signal, a first transistor connected to afirst clock input of the clocked inverter, the first transistor having agate connected to an input of the first inverter, and a secondtransistor connected between an output of the first inverter and thefirst clock input.
 13. The device of claim 12, wherein while the firstinput clock signal transitions from the first level to the thresholdlevel, the first modified clock signal is maintained at the secondlevel.
 14. The device of claim 13, wherein as the first input clocksignal reaches the second level from the threshold level, the firstmodified clock signal transitions from the third level to the firstlevel.
 15. The device of claim 12, wherein the latch circuit isconfigured to latch the inversion signal according to the first invertedclock signal.
 16. The device of claim 12, wherein the first transistoris a transistor of a first type, and the second transistor is atransistor of a second type.
 17. The device of claim 11, furthercomprising: a second clock generation circuit configured to: receive asecond input clock signal transitioning from the second level to thefirst level, and generate a second modified clock signal transitioningfrom the first level to a fourth level that is between the first leveland the second level at a third rate, in response to the second inputclock signal reaching another threshold level from the second level, andfrom the fourth level to the second level at a fourth rate less than thethird rate as the second input clock signal reaches the first level fromthe another threshold level.
 18. The device of claim 17, wherein thefirst clock generation circuit further includes: a first inverterconfigured to generate a first inverted clock signal having an oppositephase of the first input clock signal, a first transistor connected to afirst clock input of the clocked inverter, the first transistor having agate connected to an input of the first inverter, and a secondtransistor connected between an output of the first inverter and thefirst clock input; the second clock generation circuit further includes:a second inverter configured to generate a second inverted clock signalhaving an opposite phase of the second input clock signal, a thirdtransistor connected to a second clock input of the clocked inverter,the third transistor having a gate connected to an input of the secondinverter, and a fourth transistor connected between an output of thesecond inverter and the second clock input; and the clocked inverter isconfigured to generate the inversion signal, in response to the secondmodified clock signal having a voltage between the fourth level and thefirst level.
 19. The device of claim 18, wherein the latch circuit isconfigured to latch the inversion signal according to the first invertedclock signal and the second inverted clock signal.
 20. The device ofclaim 18, wherein the first transistor and the fourth transistor aretransistors of a first type, and the second transistor and the thirdtransistor are transistors of a second type.